<!DOCTYPE html>
<html>
	<head>
		
		<title></title>
	</head>
	<body>
		<script>
	function index(arr,num)
	{
	  for(var i=0;i<arr.length;i++)
	  {
		  if(arr[i]==num)
		  {
			 return i;  
		  }
	  }
	return -1;
	}
	    var b=[2,4,76,6,5,23];
	    var a=index(b,29);
	    document.write(a);
		</script>
	</body>
</html>
